If you’re looking to start an online store here are a few PHP/MySQL e-commerce softwares to consider:
Zen Cart (Opensource)
Zen Cart is an offshoot to Oscommerce which was the very first open source e-commerce software I’ve had experience with. It’s very easy to install and manage. When it comes to templates it isn’t the most aesthetically pleasing shopping cart unless you’re knowledgeable with PHP/CSS/Graphic Design. Installing plugins can be tricky and some are poorly written and may potentially conflict with existing code. However, out of the box Zen Cart works well.
X-Cart (From $195)
This is an e-commerce software developed in the Ukraine. It has loads of functionality but it’s admin panel isn’t user friendly and addons cost money. Custom development doesn’t cost much but in my opinion I would never start a project using this software unless my client requested it.
WordPress Ecommerce Plugins (free and paid plugins available)
WordPress went from being a blogging software to a full blow CMS with all sorts of free plugins that work really well and some that cost money. For a basic or startup business wordpress is great especially since it’s search engine friendly, user friendly and installing plugins is just a click of the mouse.